Patent GB-1110982-A (GB)
Title: Improvements in or relating to sewing machines
IPC: D05B65/00
Filed: 1966-04-06
Abstract: 1,110,982. Sewing machines. G. M. PFAFF A.G. 6 April, 1966 [7 April, 1965], No. 15387/66. Heading D1G A thread-carrying component of a sewing machine looptaker is coupled to drive transmission for thread-cutting mechanism by means such that said component is displaced differently during a thread drawing movement and cutting operation than in its normal movement during a sewing operation. In Figs. 1, 6 a bed shaft 13, driven by an elastic belt 12, is connected by gears 14, 15 to a shaft 16 which carries cam discs 55, 73 and is connected by gears 17, 18 to a vertical shaft (19) carrying at its upper end a rotary hook 20. A hollow shaft (26), journalled on shaft (19), is continuously driven via a gear 27 and carries at its upper end a friction wheel 29 driving a feed wheel 31 co-operating with a presser wheel (34). A bobbin case 21, journalled in the rotary hook 20, carries a lug 22 which abuts a lug 35 on the throat plate 33 to prevent rotation of the bobbin case. A lug 23 on the latter is formed with a hole for the passage of bobbin thread 25 and abuts a finger 40 carried by a sleeve 41 which is journal!ed on an eccentric fast with shaft (19) and which is formed with a pair of lugs 43 embracing a normally stationary finger 45. Sleeve 41, finger 40 and bobbin case 21 thereby oscillate together to separate lug 22 periodically from lug 35 to allow passage of the upper limb of the needle thread loop therebetween. Finger 45 is fast with a hollow shaft 46 which is journalled on shaft (26) and is connected by gears 47, 48 and a link 50 to one arm of a lever 51 pivoted on but fixed axially to an axially-slidable shaft 52. A vertically slidable rod 83 is connected at its upper end to thread-cutting blades 90, and at its lower end by a lever 81 to one arm of a lever 75 pivoted on but fixed axially to shaft 52. Pins 53 and 77, carried on the other arms of levers 51 and 75 respectively, are thereby operationally engaged with cam discs 55 and 73 respectively on leftward movement of shaft 52. A sleeve 66, fast on shaft 52, normally abuts an arm 68, pivoted on shaft 13 and biased against a collar 71 fast on the latter by a spring 70, to prevent axial movement of shaft 52. Before the machine is stopped, a treadle is actuated to swing a bell crank lever 63, via a link 65, to compress a spring 60 between a collar 59 fast on shaft 52 and a collar 61 slidable thereon. When the starting treadle is released for stopping the machine, a switch is closed in the circuit of a solenoid controlling an auxiliary drive, whereby the machine stops with the needle in the lowest position. The elasticity of belt 12 then causes a rebound of shaft 13 to disengage arm 68 from sleeve 66, whereby shaft 52 moves leftwards, against the bias of a spring 72, to engage pins 53, 77 with the cam discs 55, 73. A lug 99 on shaft 52 also actuates a reversal switch 97, whereby the machine re-starts and then stops with the needle in its highest position. Finger 40 thereby rotates bobbin case 21 to a considerable degree for drawing off bobbin thread 25, and rotary hook 20 seizes and casts off a loop of needle thread, the upper arm passing through the gap between lugs 22 and 35, and the lower arm being engaged by lug 23 to draw off a length of needle thread. Lug 22 also engages the bobbin thread, and presents both threads to the blades 90 for severing thereat. In Fig. 11 a bed shaft 102, driven by a belt 103, is connected by gears 104, 106 to a shaft 105. A threaded looper 115 is carried on an arm 113 pivoted on a pin 118 carried at one end of a bracket 120, the other end of which is pivoted on a normally-fixed pin 124. An arm 114, rigid with arm 113, has a ball and socket connection 112 with a link 111 pivoted at 110 to a pitman 108 actuated by an eccentric on shaft 105, for imparting loop seizing and shedding movements to looper 115. Bracket 120 is connected to a pitman 122 actuated by an eccentric on shaft 102 for imparting needleavoiding movements to looptaker 115. Pin 124 is rigid with an arm 126 which is pivoted at one end and slidably supports a block 128 pivoted to a crank arm 130 on a shaft 129 biased angularly by a spring 135 to engage the free end of arm 126 with a fixed abutment. A crank arm 137 on shaft 129 is connected by a link 138 to a treadle. A crank arm 140 on pin 124 has a ball and socket connection 141 to one arm of a bell crank lever 143, the other arm of which slidably supports a rod 146 which is spring-biased outwardly and which has a ball and socket connection to thread-severing means 150 slidably mounted under the work-supporting plate 101. After the machine has been stopped with the needle in the fully-raised position, shaft 129 is turned, via link 138, to pivot arm 126 downwards, whereby looptaker 115 is lowered and moved forwardly to draw off upper and lower threads, and lever 143 is turned clockwise to actuate the thread-cutting means 150.